Lift trucks and attachments therefor



Jan. 30, 1962 J. P. MORRELL 3,

LIFT TRUCKS AND ATTACHMENTS THEREFOR Filed April 29, 1959 2 Sheets-Sheet 1' & I? l l I5 IN V EN TOR.

JOHN P. MORRELL BY 1962 J. P. MORRELL 3,018, 09

LIFT TRUCKS AND ATTACHMENTS THEREFOR Filed April 29, 1959 2 Sheets-Sheet 2 INljENTOR. JOHN P. MORRELL 9km fax a ATTO N'EYS line Company, Hopkins, Minn., a corporation of Minnesota Filed Apr. 29.. 1959, Ser. No. 809,864

8 Claims. (Cl. 214-654) The present invention relates to industrial lift trucks and attachments therefor, and it particularly relates to lift trucks of the type including a set of vertically movable forks for handling objects which are of such shape as to permit them to be tiered for storage or shipment.

The present invention is described in connection with the type of truck described in US. Patent No. 2,799,417, Morrell but it will be understood by those skilled in the art that it is equally well suited to other types of fork lift trucks not necessarily including an upper clamping member for engaging the top of the object being transported and partially compressing it against the forks.

In order to transport an object with a lift truck of this general type, it is necessary to insert the lifting forks beneath the object so that they are between it and the floor or other support on which it is resting. Unless the object is supported on a special pallet itself or has an irregularly shaped bottom for accommodating the forks, it may be very difficult to insert the forks beneath it, and damage to the object might result. There are many instances where the use of pallets or other auxiliary devices are undesirable and in those cases where the object to be lifted must be turned over on its side when stacked, the use of pallets is out of the question.

Therefore, a principal object of the present invention is to provide a new and improved fork lift truck which includes means for facilitating the insertion of lifting forks beneath an object to be transported.

Another object of the present invention is to provide an attachment for industrial type lift trucks which facilitate the insertion of the forks thereof between an object to be transported and a fiat surface on which it is resting.

A further object of the present invention is to provide an auxiliary mechanism for use on fork lift trucks for facilitating the insertion of forks or the like beneath the object to be lifted, which attachment is small in size, simple in operation, and retractable to a position where it does not interfere with the normal operation of the truck.

Briefly, the above and further objects are realized in accordance with the present invention by providing a gravity operated attachment for use on fork lift trucks or the like used to tilt an object to be lifted so as to raise the corner thereof nearest the forks thereby to facilitate the insertion of the forks between the object and a supporting surface on which it is resting.

The invention, both as to its organization and method of operation, together with further objects and advan ages thereof will best be understood by reference to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a somewhat schematic perspective view of an industrial lift truck embodying the present invention;

FIG. 2 is a fragmentary elevational view showing the tilting mechanism of the present invention in an operative condition just prior to the engagement thereof with an object to be lifted;

FIG. 3 is a fragmentary elevational view similar to FIG. 2 showing the device of the present invention in op eration;

FIG. 4 is a fragmentary rear view of a portion of the device of the present invention;

FIG. 5 is an enlarged fragmentary cross sectional view of the latching mechanism used in the device of the present invention; and

ited States Patent 0 ice FIG. 6 is an enlarged fragmentary view showing a portion of the device of the present invention.

Referring now to the drawing and particularly to FIG. 1 thereof, there is shown a destacking attachment ll) of the present invention mounted on an industrial lift truck 11 which includes a control station 12 and a set of lifting forks 13 which are mounted on a set of vertical guides 1 which constitute part of the mast 15 of the truck 11. The forks 13 are relatively short and a clamp 17 is provided for cooperation with the forks 13 to clamp the object to be transported therebetween. Although the device ill may be used with any type of lift truck, these trucks are ordinarily battery operated and include a hydraulic cylinder 16 which drives the lift mechanism up and down the vertical guide posts 14 and, moreover, controls the relative positions of the clamp 17 and the forks 13.

The destacking device it) comprises as its principal elements a gripper plate 21 having a rasp-like face 22 and a plurality of supporting arms 23, 24, and 25 which, as best shown in FIG. 4, are pivotally attached at the upper ends thereof to the rear face of the gripper plate 21 and which, as best shown in FIGS. 1, 2, and 3, are pivotally attached at the lower ends thereof to a support plate 27 which is attached to the forks 13 for vertical movement therewith.

The support plate 27 is mounted in a vertical plane and inasmuch as the arms 23, 24, and 25 are of equal length the plate 21 remains in a vertical position at all times even though it is movable between the fully extended position shown in solid lines in FIG. 2 and the fully retracted position shown in phantom in FIG. 2. The support plate 27, as best shown in FIGS. 2 and 3, is mounted at a sub-- stantial distance behind the upright portions of the forks 13 so that when the plate 21 is retracted it is well behind the forks l3 and does not interfere with the normal operation of the truck 11.

In order to secure the plate 21 in the retracted position, there is provided, as best shown in FIG. 5, a latching mechanism 30 which includes a catch 3i suitably attached to the rear face of the gripper plate 21 and a spring-loaded bolt 32 suitably attached to the forward face of the supporting plate 27. The bolt 32 comprises a roller 33 secured to a piston support 34 which is mounted in a supporting cylinder 35 and biased into interlocking engagement with the catch 31 by means of a coil spring 36. Therefore, when the gripper plate 21 is moved toward the support plate 27, the catch 31 rides over the top of the roller 33 forcing it down against the spring 36 until a hook 31a on the catch 31 passes the center of the roller 33, at which time the force exerted by the spring 35 through the roller .33 locks the gripper plate 21 in the retracted position.

Inorder to release the gripper plate 21 from the locking mechanism 30, there is provided a solenoid 40 which is mounted on the rear face of the plate 27 and which includes a pusher plunger 41 slidably mounted within the field of a coil 42. The plunger 41 includes a pusher bar portion 41a which extends through an aperture 43 in the plate 27 so that when the coil 42 is energized and the enlarged core portion 41 is drawn therein, the bar 41a pushes the gripper plate 21 away from the support plate 27 thereby to pull the catch 31 out of engagement with the roller 33. Moreover, the stroke of the solenoid 40 is sufiiciently great that the gripper plate 21 is moved forward of the vertical plane in which the arms 23, 24, and 25 are pivotally attached to the support plate 27 whereby the gripper plate 21 falls under the force of gravity to the fully extended position shown in FIG. 2. The plate 21 does not fall any further than this because, as best shown in FIG. 6, the lower ends of the arms 23, 24, and 25 (only arm 23 and end 23a being shown) are so shaped as to engage the supporting 3 plate 27 and prevent further rotative movement thereof. It should be noted that the arms 23, 24 and 25 do not lie in a horizontal plane in this position.

Considering the operation of the destacking device of the present invention, let it be assumed that there is a flat bottomed object such, for example, as a carton 45 which is resting on a floor, and it is desired to lift and transport it by means of the truck 11. Accordingly, the operator actuates a suitable lever at the control station 12'; which energizes the solenoid 4G and thus unlatches the gripper plate 21 so that it falls by the force of gravity to the position shown in FIG. 2 wherein it will be noted it is forward of the leading edges of the forks 13. The truck 11 is then driven toward the carton 45 whereby the rough forward surface 22 of the gripper plate 21 engages the forward face 45a of the carton 45. As the truck 11 continues to move toward the carton 45, and assuming that the carton 45 cannot slide along the floor, the arms 23, 24 and 25 necessarily pivot in a counterclockwise direction, and since the friction face 22 of the gripper plate 21 has slightly dug into the face 45a of the carton 45, the corner 45b of the carton 45 is elevated, as shown in FIG. 3. Since the plate 21 necessarily remains in a vertical position, as the truck moves closer and closer to the carton 45, a lesser amount of the face 22 of the gripper plate 21 engages the carton 45 until the inter-engaging surfaces are insufficient to support the carton 45 and it falls. By this time the forks 13 have been inserted beneath the carton 45 so that when it falls it is on the forks 13. Thereafter, when the carton 45 is moved back against the vertical portions of the forks 13, the latch 31 on the gripper plate 21 engages the roller 33, thereby to secure the gripper plate 21 in a retracted position.

While the invention has been described in connection with a particular embodiment of the invention, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention as defined in the appended claims.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:

1. In a lift truck of the type including a lifting member insertable beneath an article to be lifted, the combination of tilting means pivotable with respect to said lifting member and having an article engaging surface extendible to a position in front of said lifting member adapted to grip said article to elevate one end of said article, means for maintaining said article engaging surface above the pivotal axis of said tilting means, and drive means for simultaneously moving said lifting member and said tilting means toward said article, whereby said tilting means engages said article and automatically pivots upwardly to lift said article over said lifting member.

2. In a lift truck of the type having at least one lifting fork insertable beneath a load for the purpose ofelevating it, the combination of a load tilting mechanism comprising a member having a gripping surface for engaging said load, means including a plurality of arms pivotally mounted to said truck and mounting said member on said truck for pivotal movement about a horizontal axis, latch means for holding said member in a retracted position behind said fork, operating means for releasing said latch means and moving said member to an extended position in front of said fork, and means including a stop on one of said arms engageable with said truck for preventing said member from falling below a horizontal plane passing through said axis, whereby movement of said truck toward said load initially causes the gripping surface on said member to engage said load and thereafter to elevate said load and permit said fork to pass beneath said load.

3. The combination set forth in claim 2 wherein said member is attached to said fork for vertical movement therewith.

4. The combination set forth in claim 2 wherein said member when released is moved from a retracted to an extended position by the force of gravity.

5. The combination set forth in claim 2 wherein said operating means comprises a solenoid having a pusher plunger operatively connected to said member only when it is in a retracted position.

6. In a lift truck of the type including a lifting member insertable beneath an article to be lifted, the combination of tilting means pivotable with respect to said lifting member and having an article engaging surface extendible to a position in front of said lifting member, said engaging surface having a rough article engaging face disposed in a plane which is at all times perpendicular to the support on which said truck is positioned, means including a stop cooperatively associated with said lifting member for maintaining said engaging surface above the pivotal axis of said tilting means, and drive means for simultaneously moving said lifting member and said tilting means toward said article whereby said engaging surface engages said article and pivots upwardly to lift said article over said lifting member.

7. In a lift truck of the type having at least one lifting fork insertable beneath a load for the purpose of elevating it, the combination of a load tilting mechanism comprising a gripper plate having a surface for gripping engagement against a surface of said load, means for moving said plate between an extended position in front of said fork to a retracted position behind said fork and upward and rearward of said extended position and including a plurality of substantially parallel supporting arms each having one end pivotally attached about a horizontal axis to said truck and each having their other end pivotally attached about a horizontal axis to said gripper plate so that said gripper plate surface remains substantially vertical during movement of said plate between said positions, latch means for holding said gripper plate in said retracted position, means for releasing said gripper plate from said retracted position so that said gripper plate moves outwardly and downwardly to said extended position, means for limiting said downward movement of said plate in said extended position before the aforesaid arms reach a horizontal plane, and drive means on said truck for advancing said truck toward said load so that said plate initially engages a side of said load and whereby further movement of said truck toward said load causes said plate to move upwardly and rearwardly of said fork thereby elevating one end of said load and tilting said load so that said fork can pass beneath said load, and whereby further movement of said truck toward said load causes said plate to release said load onto said fork.

8. The combination of a load tilting mechanism as set forth in claim 7 above wherein said gripper plate moves outwardly and downwardly from said retracted position to said extended position under the influence of gravity.

References Cited in the file of this patent UNITED STATES PATENTS 2,799,417 Morrell July 16, 1957 FOREIGN PATENTS 582,680 Great Britain Nov. 25, 1946 816,222 Germany Oct. 8, 1951 

